PORTLAND, Ore. – Deputies are following up on leads in the case of a missing 15-year-old girl believed to be with a sex abuse suspect.

Annieka Vaughan, 15, was reported as missing after she ran away from her home in Aloha on October 30, 2017, the Washington County Sheriff’s Office said.

Detectives said they think she could be with 23-year-old Zachary Petersen of Pasco, WA. He is the suspect in a sexual abuse investigation involving Annieka.

Authorities found Petersen’s pickup truck Monday morning parked in a gravel lot off of NW Cornell Road in Forest Park. Annieka’s backpack was found inside the truck, deputies said.

Later that evening, Portland Police got a call about someone hearing voices in the woods along Hemlock Trail over a mile from where the pickup was found. Officials said they aren’t sure if the report of voices was tied to Petersen and Vaughan.

A police K-9 team searched the area and the bureau’s Air Support Unit flew overhead with a thermal imaging technology, however they couldn’t find anyone.

On Tuesday, Annieka's father Rick Vaughan spoke from the Portland Police Central Precinct about the family's side of the search.

"I need her to know that people care about her and it's not about getting in trouble once we get here," he said, adding a direct message to his daughter. "You've got a lot of people that love you and care about you, people that you don't even know are supporting you and want to see you back."

Petersen is described as 5-foot 10-inches tall, about 150 pounds, with buzzed brown hair and brown eyes.

Officials initially said they think Petersen might head to the Seaside area or to Sacramento, California. Authorities in both cities are aware of the case.

The Washington County Sheriff's Office told KATU News the case is not considered to be a kidnapping because she left her home. The case does not qualify for an Amber Alert because investigators do not think she was forcefully taken.

If you have information on the whereabouts of either person, call the non-emergency dispatch at (503) 629-0111.

Anyone who has specific information on how long the pickup has been parked in the lot should email Portland Police Detective Heidi Helwig at heidi.helwig@portlandoregon.gov.